Method for performing remotely-manipulated work on a conduit of a nuclear facility

ABSTRACT

The invention is directed to a method for performing remotely-manipulated rk on a conduit of a nuclear facility. The method of the invention is for maintaining pipe conduits in a radioactively contaminated cell such as a large-area cell of a reprocessing facility for irradiated nuclear fuel. The defective conduit portion to be removed is sawn out of a conduit and a replacement conduit segment is welded into the conduit. In order to provide for rapidly and accurately welding the replacement conduit segment into the conduit, the step of machining the two conduit end portions is combined with the step of determining the inside dimension between the conduit end portions formed by the step of sawing out the defective conduit portion. An apparatus for carrying out the method of the invention is also disclosed.

This is a division of application Ser. No. 717,460, filed Mar. 29, 1985now U.S. Pat. No. 4,674,926.

FIELD OF THE INVENTION

The invention relates to a method for maintaining pipe conduits in aradioactively charged cell such as a large-area cell of a facility forreprocessing irradiated nuclear fuel. In this method, a defectiveconduit portion is cut out of the conduit by sawing and a replacementconduit segment is welded into place. The invention also relates to anapparatus for carrying out the method of the invention.

BACKGROUND OF THE INVENTION

Maintenance of the process components and the pipe conduitsinterconnecting the same must be carried out by remote control inradioactively contaminated shielded cells in the nuclear field such aslarge-area cells in nuclear reprocessing facilities. For maintaining theconduits, it can be necessary for a leaky portion of the conduit to becut out of a conduit and replaced by a replacement conduit segment whichis welded into the conduit by remote manipulation. The replacementconduit segment is prepared outside the cell and, before it can bewelded into place, the two sawn end faces of the conduit must bemachined. The replacement conduit segment must correspond in length tothe inner gap between the two end faces of the end portions of the cutconduit.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method wherein the conduitends of the cut conduit are prepared for the follow-on welding operationat low cost. The method of the invention permits a rapid and reliablepreparation of the rough-sawn conduit ends and makes it possible toinsert the replacement conduit segment therebetween with dimensionalaccuracy.

The method of the invention is for maintaining the pipe conduits of aradioactively charged cell such as a large-area cell of a reprocessingfacility for irradiated nuclear fuel wherein a portion of a conduit candevelop a leak or become otherwise defective. The method of theinvention includes the steps of: cutting the defective portion from theconduit thereby forming two mutually adjacent cut conduit end facescorresponding to respective conduit end portions; machine planing theend face of one of the conduit end portions; selecting the planed endface as a first reference point for measuring the length of the cleardimension between the conduit end portions; machine planing the end faceof the other one of the conduit end portions; selecting the planed endface of the other conduit end portion as the end reference point formeasuring the clear dimension; determining the length of the cleardimension from the reference points and preparing a replacement conduitsegment having the length of said clear dimension; remotely manipulatingthe conduit segment into the gap between the conduit end portions; and,welding the conduit segment to the conduit end portions.

According to another feature of the invention, a recessed surface ismachined into each one of the conduit end portions so as to extendaround the entire outer periphery of the end face thereof.

After the defective conduit portion has been sawn and removed, one ofthe end faces is first subjected to a machine cutting operation so as toform a clean end face and a recessed surface defining half of a weldgroove. The planed end face forms the first reference point of a lengthmeasurement distance. The end point of this length measurement distanceis the finished machined end face of the other end portion of theconduit. The longitudinal dimension which is established in this manneris used in making the replacement conduit segment.

After the operation of machining the first conduit end face, themachining unit is moved to the other conduit end face and thedisplacement of the tool is measured and the length of the replacementconduit segment is determined with the aid of this measured value.

The essential advantage of these method steps is that during the machinecutting operation on the sawn faces of the two conduit end faces, theactual dimension between these two conduit ends is ascertained at thesame time.

According to another feature of the invention, the method can includethe step of machine turning the inner wall of each of the conduit endportions while simultaneously planing the end face and machining therecessed surface into the outer periphery of the end face.

The operation of conically machine turning the conduit end portionsestablishes equal wall thicknesses with respect to that conduit endportion and the replacement conduit segment which is likewise machined.Equality of wall thickness with respect to the mutually butting endfaces of the conduit end portion and conduit segment is a requirementfor the necessary follow-on automatic welding operation.

It is another object of the invention to provide an apparatus with whichthe rough-sawn conduit ends can be rapidly and reliably prepared fordimensionally accurately welding the replacement conduit segment intoposition.

The apparatus of the invention includes a connecting carrier beam; clampconnecting means for clamping said carrier beam to the conduit endportions so as to fix the position of the carrier beam with respect tothe end portions; a machining unit for machining the end faces of theconduit end portions; a carriage movably mounted on the carrier beam forcarrying the machining unit and for moving the same between the endfaces; and, detecting means for detecting the distance through which themachining unit is moved by the carriage.

The connecting carrier beam is arranged parallel to the cut conduitafter the apparatus has been clamped thereto. The carriage moves themachining unit between the two conduit ends and the distance covered bythe machining unit is measured.

The threaded spindle has a known pitch and the revolutions of thespindle are detected by detector means in the form of a rotationdetector during the displacement of the carriage. The length of thedistance covered by the carriage is determined from the measurementsmade in this fashion.

According to another feature of the invention, the machining unitincludes a drive shaft and two cutter heads mounted on respective endsof the drive shaft for machining corresponding ones of the conduit endportions; and, each of the cutter heads includes a plurality of cuttingtools. With the apparatus of the invention configured in this manner,the distance traversed by the carriage is smaller than the actual gap inthe conduit by an amount equal to the spacing between the two cutterheads. That spacing is known by virtue of the design configuration ofthe machining unit and can therefore be added to the measured length ofthe distance travelled by the carriage and machining unit. The result ofthis addition corresponds to the length of the required replacementconduit segment which is to be welded into position. This embodimentaffords the advantage that the apparatus for machining the oppositelydisposed conduit ends is of simple configuration.

Three pairs of cutting tools are disposed in each cutter head andperform three different machining operations at the same time in oneworking step.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described with reference to the drawingwherein:

FIG. 1 is a view of the arrangement of the invention for preparing thesawn end faces of the conduit end portions for the welding operation;

FIG. 2 is an end view of the arrangement of FIG. 1 showing one of theclamping devices about to clamp onto a conduit end portion;

FIG. 3 shows a front elevation view of a cutter head;

FIG. 4 is a side elevation view of the cutter head with the front endportion of the housing broken away to show the cutting tools; and,

FIG. 5 is a side elevation view, in longitudinal section, through oneconduit end portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The arrangement shown in FIG. 1 includes a beam-like connecting carrier6 and clamping assemblies 7 and 8 mounted at the two ends thereof. Guiderails 9 are mounted on the connecting carrier 6 and extend over theentire length thereof, on both sides. A carriage 11 is movably mountedon the guide rails 9. The carriage 11 is movable along the connectingcarrier 6 by means of a threaded spindle 12 which is rotatably driven byan electric motor.

An electric motor 13 is suspended on the carriage 11 and has an outputshaft which extends therethrough and which carries cutter heads 14 and15 on respective ends thereof. Cutting tools required for machining theconduit ends are mounted in the heads 14 and 15.

The clamping assemblies 7 and 8 carry the respective clamping units 21and 22. The clamping unit 21 includes two geared motor units 23, 24 anda pair of clamping levers 26, 27. Likewise, the clamping unit 22includes two geared motor units of which one unit 25 is shown and a pairof clamping levers for which one lever 28 is shown. The two clampinglevers of each pair are rotatable about a common axis defined by a pinwhich for the clamping levers 26 and 27 is identified by referencenumeral 29. The pin 29 is centrally mounted in an intermediate piece 31disposed at the lower end of the clamping assembly. The same arrangementis provided for clamping assembly 8 of which one motor unit 25 and oneclamping lever 28 is shown in FIG. 1.

The motor units 23, 24 are attached to the sides of the intermediatemember 31 and have downwardly movable pressure spindles for acting onthe levers 26 and 27, respectively.

One of the levers 26 of a pair of levers 26, 27 has a clamping surface41 while the other lever 27 has two pressure plates 42 and 43 which areangularly spaced relative to each other by 90°. The clamping assembliestherefore provide a three-point clamping action for holding the conduitends 44 or 45.

The entire apparatus can be picked up and transported at a handlingblock 46 by means of a power manipulator or by means of a block andtackle crane.

The cutter heads 14 and 15 are respective tool carriers in which thecutting tools required for machining the conduit ends are fitted. FIG. 3shows a front elevation view of the cutter head 15.

There are three pairs of cutting tools. Cutting tools 51 and 52constitute a first pair of cutting tools and are mounted on the innerperiphery of the cutter head 15 so as to be diametrically opposite eachother. The cutting tools 51 and 52 are radially positioned in such a waythat they can be used to produce the half 71 (FIG. 1) of a weld groovewhich is desired at the outside periphery of the conduit end 45.

Cutting tools 54 and 55 constitute a second pair of cutting tools andare disposed at 90° with respect to the first pair of cutting tools 51and 52. The second pair of cutting tools 54 and 55 plane the end face ofthe conduit end 45.

Cutting tools 56 and 57 constitute a third pair of cutting tools and arearranged on the center shaft of the cutter head 15 so as to bediametrically opposite each other. In addition, when viewed in the axialdirection, the third pair of cutting tools is disposed in front of thefirst and second pairs of cutting tools (51, 52) and (54, 55),respectively, as shown in FIG. 4. The cutting tools 56 and 57 turn theinside wall surface of the conduit end 45. The cutter head 14 is of thesame configuration as cutter head 15.

The operation of the above-described apparatus will now be described.

After a conduit portion has been sawn out of a conduit by remotelymanipulated equipment, the apparatus of the invention is picked up by apower manipulator at the handling block 46 and taken to the conduit atthe location thereof where the conduit portion was removed. Theoperation of sawing out the conduit segment has left two mutuallyadjacent conduit ends 44 and 45 having respective end faces in arough-sawn condition. The apparatus is placed with its opened pair ofclamping levers 26, 27 of clamping assembly 7 on conduit end 44 and withits open pair of clamping levers of clamping assembly 8 on conduit end45. The arrangement of the invention is firmly clamped in position onthe conduit ends 44 and 45 by actuating the electric motor units 23, 24and the two motor units of clamping assembly 8. When that is done, theconduit ends 44 and 45 are in alignment with each other.

The spindle 12 for moving the carriage 11 is driven in rotation by meansof an electric motor so that the carriage 11 with the machining unit(13, 14, 15) is moved against the one conduit end 44. Now, in oneworking operation at this conduit end 44, the end face 58 is planed withthe pair of cutting tools 54, 55, one half 53 of a weld groove ismachined onto the periphery of the conduit end by means of the pair ofcutting tools 51, 52 and the inner wall of the conduit end 44 isprovided with a tapering peripheral surface 61 (FIG. 5) which narrowsinwardly by the machine turning action of the pair of cutting tools 56and 57.

After that machining operation has been concluded, the threaded spindle12 is rotated in the opposite direction and the revolutions thereof aredetected and evaluated by means of a rotation sensor 62, for example aninductive rotation sensor. The machining unit (13, 14, 15) is moved awayfrom the machined conduit end 44 and driven to the other rough-sawnconduit end 45 where the same machining operation is carried out. Thatoperation results in the formation of a weld groove half 71 which is inmirror image relationship to the half 53 on conduit end 44.

After the machining operation on conduit end 45 has been completed, thedimension between the two machined end faces 58 of the two conduit ends44 and 45 is detected by means of the rotations of the threaded spindle12 and displayed. It is now possible to produce a replacement conduitsegment outside of the cell having exactly the required length and whichprecisely corresponds to the clear dimension between the two machinedconduit ends 44 and 45 and which has parallel weld edges which, with therespective peripheral recess surfaces 53 and 71, define two weldgrooves. This replacement conduit segment is moved withremotely-controlled equipment into a position between the two conduitends 44 and 45 and is welded in position with remotely-controlledapparatus.

It is understood that the foregoing description is that of the preferredembodiments of the invention and that various changes and modificationsmay be made thereto without departing from the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:
 1. A method for maintaining the pipe conduits of aradioactively charged cell of a reprocessing facility for irradiatednuclear fuel wherein a portion of a conduit can develop a leak or becomeotherwise defective, the method comprising the steps of:cutting thedefective portion from the conduit thereby forming two mutually adjacentcut conduit end faces corresponding to respective conduit end portions;tightly clamping said end portions to align the same with respect toeach other; moving a machining unit to the end face of one of theconduit end portions and machine planing said one end face; selectingthe planed end face as a first reference point for measuring the lengthof the clear dimension between said conduit end portions; displacing themachining unit to the end face of the other one of said conduit endportions and machine planing said end face of said other conduit endportion; selecting the planed end face of said other conduit end portionas the end reference point for measuring said clear dimension; measuringthe displacement of the machining unit from said first reference pointto said end reference point; determining the length of said cleardimension and therefore of a replacement conduit segment with the aid ofthe measured value of said displacement; preparing said replacementconduit segment having said length; remotely manipulating said conduitsegment into the gap between said conduit end portions; and, weldingsaid conduit segment to said conduit end portions.
 2. The method ofclaim 1, comprising the further steps of: machining a recessed surfaceinto said one conduit end portion so as to extend around the entireouter periphery of the end face thereof to define one surface of a firstweld groove; and,machining a recessed surface into said other conduitend portion so as to extend around the entire outer periphery of the endface thereof to define one surface of a second weld groove.
 3. A methodfor maintaining the pipe conduits of a radioactively charged cell of areprocessing facility for irradiated nuclear fuel wherein a portion of aconduit can develop a leak or become otherwise defective, the methodcomprising the steps of:cutting the defective portion from the conduitthereby forming two mutually adjacent cut conduit end facescorresponding to respective conduit end portions; moving a machiningunit to the end face of one of the conduit end portions and machineplaning said end face; selecting the planed end face as a firstreference point for measuring the length of the clear dimension betweensaid conduit end portions; moving said machining unit from said end faceof said one conduit end portion to said end face of said other conduitend portion; machine planing the end face of said other one of saidconduit end portions; selecting the planed end face of said otherconduit end portion as the end reference point for measuring said cleardimension; measuring the displacement of said machining unit after saidend face of said other conduit end portion has been machined;determining the length of said clear dimension and therefore of areplacement conduit segment with aid of the measured value of saiddisplacement; preparing said replacement conduit segment having saidlength; remotely manipulating said conduit segment into the gap betweensaid conduit end portions; and, welding said conduit segment to saidconduit end portions.
 4. The method of claim 3, wherein said machiningunit has two cutter heads disposed directly opposite each other at apredetermined spacing therebetween for machining respective ones of saidend faces and wherein said machining unit is mounted on a carriage formoving said machining unit between said end faces; the method comprisingthe further steps of:moving said carriage with said machining unit fromthe end face of said one conduit end portion to the end face of saidother conduit end portion; determining the displacement of said carriageafter the end face of said other one of said end portions has beenmachined and applying said spacing to the measured value of saiddisplacement for determining said length of said conduit segment.
 5. Themethod of claim 4, the method further comprising the step of machineturning the inner wall of each one of said conduit end portions whilesimultaneously planing the end face and machining said recessed surface.